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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Influence of Charge Distribution on Structural Changes of Aromatic Imide Derivatives upon One-Electron Reduction Revealed by Time-Resolved Resonance Raman Spectroscopy during Pulse Radiolysis
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Influence of Charge Distribution on Structural Changes of Aromatic Imide Derivatives upon One-Electron Reduction Revealed by Time-Resolved Resonance Raman Spectroscopy during Pulse Radiolysis

机译：电荷分布对脉冲辐射时间分辨共振拉曼光谱揭示芳香酰亚胺衍生物结构变化的影响

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摘要

Structural changes of aromatic imides upon one-electron reduction are investigated by time-resolved resonance Raman spectroscopy during pulse radiolysis. Significant downshifts are observed for both the aromatic ring stretching and carbonyl stretching modes, which are related to a reduction of the bond order and increase of the charge density on these moieties. For three aromatic imides, i.e., 1,8 -naphthalene imide (1,8-NI), 2,3-naphthalene imide (2,3-NI), and naphthalene diimide (NDI), the extent of structural changes is found to follow the order: 2,3-NI 1,8-NI NDI, reflecting the influence of charge distribution on molecular structure. To further investigate this phenomenon, a series of homologous NDI derivatives with a substituted phenyl group at the imide position are studied. The Raman peaks between 1550 and 1600 cm(-1) which are assigned to aromatic stretching vibrations of the NDI moieties, are found to be sensitive to the charge distribution: stronger electron-withdrawing substituents result in these peaks shifting to slightly higher wavenumbers. As supported by a spin density analysis, despite the fact that the added charge is mostly localized on the NDI moiety, in the presence of an electron-withdrawing group, the subtle charge is likely to delocalize on the phenyl fragment, alleviating the effect of one-electron reduction on the molecular structure.
机译：在脉冲辐射期间通过时间分辨的共振拉曼光谱研究了芳族酰亚胺的结构变化。对于芳环拉伸和羰基拉伸模式，观察到显着的降档，其与减少键合令和这些部分上的电荷密度的增加有关。对于三个芳族酰亚胺，即1,8-萘酰亚胺（1,8-Ni），2,3-萘酰亚胺（2,3- Ni）和萘二酰亚胺（NDI），发现结构变化的程度按顺序：2,3-Ni＆ 1,8-ni＆ NDI，反映了电荷分布对分子结构的影响。为了进一步研究这种现象，研究了酰亚胺位置处具有取代苯基的一系列同源NDI衍生物。将在1550至1600cm（-1）之间的拉曼峰被分配给NDI部分的芳族拉伸振动，对电荷分布敏感：较强的吸电子取代基导致这些峰移至稍高的波数。由于旋转密度分析支持，尽管增加了电荷大部分在NDI部分上局部化，但在释放电子基团的存在下，微妙的电荷可能会在苯基片段上删除，减轻一个人的效果 - 电子降低分子结构。

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